Transmission of acknowledgement signals

ABSTRACT

Methods are described for a Node B to transmit and for a User Equipment (UE) to receive ACKnowledgement (ACK) information associated with the use of Hybrid Automatic Repeat reQuest (HARM), also known as HARQ-ACK signaling, in a communication system that includes multiple downlink component carriers or multiple uplink component carriers. An HARQ-ACK signal to a UE is in response to a data packet transmission from the UE and may consist of 2 information bits when the UE has 2 or more transmitter antennas. The HARQ-ACK signal is always located in the same downlink component carrier as the scheduling assignment resulting to the data packet transmission from the UE.

PRIORITY

This application is a Continuation Application of U.S. application Ser.No. 12/684,419 which was filed in the U.S. Patent and Trademark Officeon Jan. 8, 2010 and claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application No. 61/153,069, entitled “Transmission ofAcknowledgement Signals”, which was filed in the U.S. Patent andTrademark Office on Feb. 17, 2009, the contents of each of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to wireless communication systems and,more specifically, to the transmission of acknowledgement signals inresponse to the reception of respective data packets.

2. Description of the Art

The DownLink (DL) of a communication system transmits signals from aserving base station (Node B) to User Equipments (UEs) over an operatingBandWidth (BW). The DL signals include data signals that provide thedata information, control signals that provide control information forthe scheduling of data signals, and Reference Signals (RS), also knownas pilot signals, that enable coherent demodulation of data or controlsignals. The DL data signals are transmitted through the PhysicalDownlink Shared CHannel (PDSCH).

The UpLink (UL) of a communication system transmits signals from UEs totheir serving Node B. The UL signals also include data signals, controlsignals and RS. The UL data signals are transmitted through the PhysicalUplink Shared CHannel (PUSCH). In the absence of PUSCH transmission, aUE transmits its UL Control Information (UCI) through the PhysicalUplink Control CHannel (PUCCH); otherwise the UE may transmit the UCIthrough the PUSCH.

A UE, also commonly referred to as a terminal or a mobile station, maybe fixed or mobile and may be a wireless device, a cellular phone, apersonal computer device, etc. A Node B is generally a fixed station andmay also be referred to as a Base Transceiver System (BTS), an accesspoint, or some other terminology.

An exemplary multiplexing method for DL signal transmissions is theOrthogonal Frequency Division Multiple Access (OFDMA), and an exemplarymultiplexing method for UL signal transmissions is the Single-CarrierFrequency Division Multiple Access (SC-FDMA), as they are alsoconsidered in the 3GPP Long Term Evolution (LTE). These multiplexingmethods serve only to illustrate applications and are not restrictive tothe present invention.

DL control signals transmitted through the physical layer may be ofbroadcast or UE-specific (unicast) nature. Broadcast control signalsconvey system information to all UEs. The system information may betransmitted in different broadcast channels having differenttransmission rates depending on how quickly the broadcast controlinformation should be obtained by the UEs. For example, a BroadcastCHannel (BCH) may consist of a Primary BCH (P-BCH) and a Secondary BCH(S-BCH). UE-specific control signals convey Scheduling Assignments(SAs), for PDSCH reception (DL SAs) or PUSCH transmission (UL SAs) byUEs, and ACKnowledgement (ACK) and Negative ACKnowledgement (NAK)signals associated with the use of Hybrid Automatic Repeat reQuest(HARM) for PUSCH transmissions (HARQ-ACK signals). The Node B transmitsto a UE a HARQ-ACK signal with a positive (ACK) or negative (NAK)information value, in response to a correct or incorrect PUSCHreception, respectively. The Node B transmits the HARQ-ACK signalsthrough the Physical Hybrid-ARQ Indicator CHannel (PHICH). The DL SAs,the UL SAs, the PHICH, and possibly other control channels, are conveyedfrom the Node B to UEs through the Physical Downlink Control CHannel(PDCCH).

An exemplary PDCCH transmission structure in the DL Transmission TimeInterval (TTI), which for simplicity is assumed to consist of onesub-frame having M OFDM symbols, is shown in FIG. 1. The PDCCH 120occupies the first N OFDM symbols 110. The Node B informs the UEs of thePDCCH size through the transmission of a Physical Control FormatIndicator CHannel (PCFICH) in the first OFDM symbol (not shown forsimplicity). The remaining M-N OFDM symbols are primarily used for PDSCHtransmission 130. The PHICH 140 is transmitted in some PDCCHsub-carriers, also referred to as Resource Elements (REs), which may beplaced only in the first PDCCH symbol or in all PDCCH symbols as inFIG. 1. Some OFDM symbols also contain RS REs, 150 and 160, for each ofthe Node B transmitter antennas which in FIG. 1 are assumed to be two.The PHICH REs are grouped in consecutive REs with only RS REs possiblybeing placed between PHICH REs. Each group of PHICH REs consists of 4REs and will be referred to as Resource Element Group (REG). A group of12 consecutive REs 170 will be referred to as a Physical Resource Block(PRB). For the present example, both the DL BW and the UL BW includePRBs and the respective PDSCH and PUSCH transmissions occur over aninteger number of PRBs. For example, an UL BW of 18 MHz consists ofN_(RB) ^(UL)=100 PRBs of 180 KHz with the PRBs indexed from 0 up toN_(RB) ^(UL)−1.

The PHICH resource used for an HARQ-ACK signal transmission is assumedto be linked to the PRBs used for the respective PUSCH transmission.Therefore, the PHICH resources depend in principle on the total numberof PRBs, N_(RB) ^(UL), in the UL operating BW. When multiple PRBs areallocated to a PUSCH transmission, the PHICH resource is determined fromthe PRB with the lowest index I_(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index)(first PRB for a PUSCH transmission).

Spatial Division Multiple Access (SDMA) is an effective technique forimproving UL spectral efficiency. With SDMA, some PRBs are shared byPUSCH transmissions from multiple UEs. SDMA is facilitated by providingorthogonal RS to the respective UEs so that the Node B can obtain anaccurate estimate for the channel response experienced by each PUSCHtransmission. Using SC-FDMA for PUSCH transmissions, the RS is assumedto be constructed from a Constant Amplitude Zero Auto-Correlation(CAZAC) sequence. Orthogonal RS can then be obtained by applyingdifferent Cyclic Shifts (CS) to the CAZAC sequence representing the RS,or by applying Orthogonal Covers (OC) in the time domain in case of 2 ormore RS in the PUSCH. Each UE is informed of the CS, OC, or both, toapply to a CAZAC sequence for the RS transmission in the PUSCH throughthe CS Indicator (CSI) Information Element (IE) provided in the UL SA(the CSI may also indicate a OC used together with a specific CS).

Since PUSCH PRBs are shared among multiple SDMA UEs, using only I_(PRB)_(—) _(RA) ^(lowest) ^(—) ^(index) to determine the PHICH resource foreach respective HARQ-ACK signal transmission may lead to collisions asthe same PHICH resource may correspond to multiple SDMA UEs if they havethe same I_(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index) for their PUSCHtransmissions. This problem is avoided by having the CSI IE serve notonly to assign the CS, or OC, or both, for the RS transmission in thePUSCH but also for adjusting the resource for the respective PHICHtransmission.

FIG. 2 illustrates the use of the CSI IE for adjusting the resource of aPHICH transmission where the UL operating BW consists of N_(RB)^(UL)=100 PRBs 210, there are 4 SDMA UEs, and the PUSCH transmission BWis 10 PRBs with the lowest PRB index being equal to 8 220. Assuming thatthe CSI IE consists of 3 bits, the 8 CSI values can map to 8 respectiveincremental shifts, including a zero shift, for the PHICH resourcerelative to the one obtained from I_(PRB) _(—) _(RA) ^(lowest) ^(—)^(index). By respectively assigning to the first, second, third, andfourth UEs the first four CSI values, CSI 0 232, CSI 1 234, CSI 2 236,and CSI 3 238, the respective PHICH indexes are PHICH 1=8 242, PHICH 2=9244, PHICH 3=10 246, and PHICH 4=11 248. This approach requires that thenumber of SDMA UEs is less than or equal to the number of PRBs assignedto their PUSCH transmissions which is typically the case in practice.

It is desirable that each HARQ-ACK signal is not confined in only one REbut is instead spread over all REs in each REG to obtain interferencerandomization. To avoid reducing the multiplexing capacity of the PHICH(by a factor of 4 in FIG. 1), orthogonal multiplexing of the PHICH mayapply within each REG using, for example, Walsh-Hadamard (WH) orthogonalsequences with Spreading Factor (SF) of N_(SF) ^(PHICH) (where, in FIG.1, N_(SF) ^(PHICH)=4). For Quadrature Phase Shift Keying (QPSK)modulation and HARQ-ACK signals conveying a binary value (ACK or NAK),each PHICH channel may be placed on the In-phase (I) or Quadrature (Q)QPSK component and be further modulated with an orthogonal sequence overeach REG. For example, for a REG consisting of 4 REs and orthogonalsequences with N_(SF) ^(PHICH)=4, the PHICH multiplexing capacity (PHICHresources) for HARQ-ACK signals with binary values is 2N_(SF) ^(PHICH)=8(obtained from a factor of 2 from the I/Q dimensions of QPSK times a SFof N_(SF) ^(PHICH)=4 from the number of orthogonal sequences over theREG of 4 REs).

FIG. 3 illustrates a HARQ-ACK signal transmission from the Node B in oneof the PHICH resources available within one REG consisting of 4 REs. AnHARQ-ACK bit 310 is multiplied in multipliers 322, 324, 326, and 328, byeach element of the WH sequence 332, 334, 336, and 338 and the resultingoutput is placed on the I-branch of the QPSK modulated RE 342, 344, 346,and 348 (the Q-branch may be used for the HARQ-ACK bit for another UE).The WH sequence may be one of the 4 WH sequences 350. With I/Qmultiplexing and orthogonal sequence multiplexing with N_(SF)^(PHICH)=4, 8 PHICH channels are provided within one REG. The UEreceiver needs to only perform the conventional functions of QPSKdemodulation and orthogonal sequence despreading (and averaging over therepeated PHICH group transmissions as discussed below).

The HARQ-ACK signal transmission in each PHICH group may be repeatedover multiple REGs to obtain frequency diversity and improve theeffective Signal-to-Interference and Noise Ratio (SINR).

FIG. 4 illustrates the repetition for the HARQ-ACK signal transmissionin 3 PHICH groups, 412, 414, and 416, over 3 respective REGs, {422, 424,426}, {432, 434, 436}, and {442, 444, 446} in the same OFDM symbol(different OFDM symbols may also be used as in FIG. 1). The number ofsymbols used for the PHICH transmission defines the duration of thePHICH transmission which can be indicated to UEs through the P-BCH. Forexample, a 1-bit value in the P-BCH can indicate whether the PHICHtransmission is in 1 or 3 OFDM symbols.

Multiple PHICH resources mapped to the same set of REs in one or moreREGs constitute a PHICH group. PHICH resources in the same PHICH groupare separated through I/Q multiplexing and through different orthogonalsequences. A PHICH resource is identified by the index pair (n_(PHICH)^(group), n_(PHICH) ^(seq)), where n_(PHICH) ^(group) is the PHICH groupnumber and n_(PHICH) ^(seq) is the orthogonal sequence index within thegroup. The number of PHICH groups is given by N_(PHICH)^(group)=┌N_(g)(N_(RB) ^(DL)/8)┐ where N_(g)ε{1/6,1/2,1,2} is aparameter identified to UEs through the P-BCH and the ┌ ┐ operationrounds a number to its next integer. It is assumed that the total numberof DL PRBs, N_(RB) ^(DL), is known by the UEs prior to any PHICHreception while the total number of UL PRBs, N_(RB) ^(UL), may not beknown. For this reason, N_(RB) ^(DL)(not N_(RB) ^(UL)) is used tospecify N_(PHICH) ^(group). The PHICH group number is determined byEquation (1).

n _(PHICH) ^(group)=(I _(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index)+CSI)mod N _(PHICH) ^(group)  (1)

The orthogonal sequence index within the group is determined by Equation(2)

n _(PHICH) ^(seq)=(└I _(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index) /N_(PHICH) ^(group) ┘+CSI)mod 2N _(SF) ^(PHICH)  (2)

In Equation (2), the └ ┘ operation rounds a number to its previousinteger. PHICH resources corresponding to consecutive PRBs are mapped todifferent PHICH groups.

In order to support higher data rates than possible in legacycommunication systems, for aggregation of multiple Component Carriers(CCs) is typically considered in both the DL and UL of the communicationsystem to provide higher operating BWs. For example, to supportcommunication over 100 MHz, aggregation of five 20 MHz CCs can be used.For ease of reference, UEs capable of operating only over a single CCwill be referred to as “legacy-UEs” while UEs capable of operating overmultiple CCs will be referred to as “advanced-UEs”. From a set ofmultiple DL CCs or UL CCs, an advanced-UE may be assigned PDSCHreception or PUSCH transmission, respectively, only in a sub-set of DLCCs or UL CCs.

FIG. 5 further illustrates the principle of CC aggregation in theexemplary case of DL CCs. This principle can be extended in the samemanner for UL CCs. An operating BW of 100 MHz 510 is constructed by theaggregation of 5 (contiguous, for simplicity) DL CCs, 521, 522, 523,524, 525, each having a BW of 20 MHz. As for the sub-frame structure fora single DL CC in FIG. 1, the sub-frame structure in the case ofmultiple DL CCs consists of a PDCCH region, such as for example 531through 535, and a PDSCH region, such as for example 541 and 545. ThePDCCH region size may vary per DL CC and its value is signaled by therespective PCFICH. For CCs 1 and 5, the PDCCH size is respectively,PDCCH-1=3 symbols 531 and PDCCH-5=1 symbol 535. Since the PDSCH size isfound by subtracting the respective PDCCH size from the sub-frame size,PDSCH-1=11 symbols 541 and PDSCH-5=13 symbols 545.

FIG. 5 also illustrates the extension of the PDCCH design for SAtransmissions to advanced-UEs. Scheduling is assumed to be independentamong CCs and each PDCCH is contained within one CC regardless of thenumber of CCs an advanced-UE may use for PDSCH reception or PUSCHtransmission. The advanced-UE 550 receives two distinct SAs, SA2 552 andSA3 553, for respective PDSCH reception in the second and third CCs,while the advanced-UE 560 receives SA5 565 for PDSCH reception in thefifth CC. Different Transport Blocks (TBs) are associated with differentSAs. Each SA scheduling PDDCH reception in a DL CC or PUSCH transmissionin an UL CC that is either linked to the DL CC with the SA transmissionor indicated by the SA, may be transmitted in the same DL CC or in adifferent DL CC.

The examples used herein consider a communication system using CCaggregation and investigates aspects regarding the mapping of PHICHresources. Having a variable number of DL CCs and UL CCs configured foran advanced-UE necessitates a different mapping for the PHICH resourcesfor advanced-UEs relative to the one for legacy-UEs. Moreover, as the DLoperating BW may be substantially greater than the UL operating BW, itis desirable that the dimensioning of PHICH groups is not based on thetotal number of DL PRBs. Also, unlike legacy-UEs for which PUSCHtransmission is assumed to be limited to one CodeWord (CW) or one TB,resulting in one respective HARQ-ACK information bit in the DL,transmission of two CWs or two TBs, each using a separate HARQ process,may apply for advanced-UEs having two transmitter antennas through theapplication of Spatial Multiplexing (SM). Then, support for two HARQ-ACKinformation bits is required.

Therefore, there is a need to map PHICH resources for advanced-UEshaving multiple configured DL CCs and UL CCs.

There is also a need to avoid over-dimensioning the number of PHICHgroups in order to avoid unnecessarily increasing the respective DLoverhead.

There is also another need to efficiently support 2-bit HARQ-ACK signaltransmission while avoiding PHICH collisions.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been designed to solve at leastthe aforementioned limitations and problems in the prior art and thepresent invention provides methods for the transmission by a Node B andfor the reception by a UE of HARQ-ACK signals through a PHICH inresponse to PUSCH transmissions by the UE in a communication systemconsisting of multiple DL CCs or multiple UL CCs.

In accordance with a first embodiment of the present invention, the NodeB always transmits and the UE always receives the HARQ-ACK signal andthe Scheduling Assignment (SA), for the respective PUSCH transmission bythe UE, in the same DL CC.

In accordance with a second embodiment of the present invention, whenmore than one UL CCs are associated with a single DL CC, the number ofresource blocks in all these UL CCs is jointly considered in the mappingdetermination of the resource for PHICH transmission.

In accordance with a third embodiment of the present invention, thePHICH is transmitted only in a subset of the DL CCs of the communicationsystem.

In accordance with a fourth embodiment of the present invention, for aHARQ-ACK signal transmission conveying 2 information bits in response toa PUSCH transmission over at least 2 resource blocks, the PHICH resourcefor the first HARQ-ACK information bit depends on the number of thefirst PRB and the PHICH resource for the second HARQ-ACK information bitdepends on the number of the second PRB. Alternatively, for PUSCHtransmission over at least N_(PHICH) ^(group)+1 PRBs, the PHICH resourcefor the first HARQ-ACK information bit is determined from the number ofthe first PRB and the PHICH resource for the second HARQ-ACK informationbit is determined from the number of the N_(PHICH) ^(group)+1 PRB.

In accordance with a fifth embodiment of the present invention, for aHARQ-ACK signal transmission conveying 2 information bits in response toa PUSCH transmission from at least 2 UE transmitter antennas, the PHICHresource for the first HARQ-ACK information bit is determined from aparameter of the Reference Signal (RS) from the first antenna and thePHICH resource for the second HARQ-ACK information bit is determinedfrom a parameter of the RS from the second antenna.

In accordance with a sixth embodiment of the present invention, thePHICH resources are determined using a parameter with a first value fora first type of UEs and using the same parameter with a second value fora second type of UEs. Additionally, the second parameter value may bedetermined by the second type of UEs in conjunction with the firstparameter value using additional bits in a broadcast channel where theseadditional bits are not utilized by the first type of UEs.

In accordance with a seventh embodiment of the present invention, thePHICH resources are indicated to UEs through a broadcast channel in afirst set of DL CCs and through higher layer signaling in a second setof DL CCs.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating an exemplary DL sub-frame structure forPDCCH, PDSCH, and PHICH transmissions in the DL of the communicationsystem;

FIG. 2 is a diagram illustrating the use of the CSI IE for adjusting theresource of a PHICH transmission;

FIG. 3 is a block diagram illustrating the HARQ-ACK signal transmissionfrom the Node B in one of the PHICH resources available within one REGconsisting of 4 REs;

FIG. 4 is a diagram illustrating the repetition for the HARQ-ACK signaltransmission in 3 PHICH groups;

FIG. 5 is a diagram illustrating the principle of component carrieraggregation;

FIG. 6 is a diagram illustrating the transmission of UL SAs in 5 DL CCs;

FIG. 7 is a diagram illustrating the mapping of PHICH resources tomultiple DL CCs when a one-to-one mapping applies between an UL CC and aDL CC;

FIG. 8 is a diagram illustrating the mapping of PHICH resources whenmore than one UL CCs are associated with a single DL CC;

FIG. 9 is a diagram illustrating the mapping of PHICH resources whenmore than one DL CCs are associated with a single UL CC;

FIG. 10 is a diagram illustrating the mapping of PHICH resources whenmore than one DL CCs are associated with a more than one UL CCs;

FIG. 11 is a diagram illustrating a first PHICH resource mapping forPUSCH transmission including 2 CWs (or 2 TBs);

FIG. 12 is a diagram illustrating a second PHICH resource mapping forPUSCH transmission including 2 CWs (or 2 TBs);

FIG. 13 is a diagram illustrating the use of a sub-set of DL CCs toestablish the communication link; and

FIG. 14 is a diagram illustrating the dimensioning of PHICH resourcesusing bits in the P-BCH that are interpreted by advanced-UEs jointlywith existing bits in the P-BCH.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the scope of the invention to those skilled in the art.

Additionally, although the present invention is described in relation toan Orthogonal Frequency Division Multiple Access (OFDMA) communicationsystem, it also applies to all Frequency Division Multiplexing (FDM)systems in general and to Single-Carrier Frequency Division MultipleAccess (SC-FDMA), OFDM, FDMA, Discrete Fourier Transform (DFT)-spreadOFDM, DFT-spread OFDMA, SC-OFDMA, and SC-OFDM systems in particular.

The invention considers that an advanced-UE is semi-statically assignedthe CCs over which it may perform PDSCH reception (DL CCs) or PUSCHtransmission (UL CCs). The transmission of DL SAs or UL SAs to anadvanced-UE is only over one or more DL CCs of PDSCH reception. Adifferent TB is associated with each DL SA or UL SA. A DL SA may addressPRBs for the associated PDSCH reception in only one DL CC or in multipleDL CCs. Similarly, an UL SA may address PRBs for the associated PUSCHtransmission in only one UL CC or in multiple UL CCs. In order toassociate one or more UL CCs with the UL SA transmitted in one or moreDL CCs, respectively, a one-to-one mapping can be preconfigured betweenthe DL CCs of the UL SA transmission and the UL CCs of PUSCHtransmission or explicit indexing can be included in the UL SA toindicate the UL CCs for PUSCH transmission.

An advanced-UE is assumed to be assigned, among its DL CCs, a primary DLCC. The primary DL CC serves as a reference relative to the remaining,secondary, DL CCs. For example, referring to FIG. 5, DL CC2 may be theprimary DL CC for advanced-UE1 while DL CC3 is a secondary DL CC. Thesecondary DL CCs may also be ordered, in which case the DL CCs can bereferred to as primary, first secondary, second secondary, and so on.Equivalently, the DL CCs may be ordered as first DL CC, second DL CC,and so on, and a DL SA or an UL SA is always transmitted in the first DLCC. For simplicity, the “primary” and “secondary” terminology will beused but the “first”, “second” and so on terminology may also apply.

FIG. 6 further illustrates the transmission of UL SAs in 5 CCs. Thetransmission of DL SAs can be performed in the same manner (not shown).The first DL CC 611 supports UL SA transmissions only to legacy-UEs,such as L-UE₁ 621 and L-UE_(K) 622. The second 612 and third 613 DL CCssupport UL SA transmissions to a mixture of advanced-UEs, such as A-UE₁having UL SAs 623 and 625, and legacy-UEs, such as L-UE_(L) and L-UE_(M)having respective UL SAs 624 and 626. A-UE₁ has 2 DL CCs. The primary DLCC is DL CC2 and the secondary DL CC is DL CC3. DL CC4 614 also supportsa mixture of advanced-UEs and legacy-UEs while DL CC5 615 supports onlyadvanced-UEs. A-UE₂ also has 2 DL CCs. The primary DL CC is DL CC4 andthe secondary DL CC is DL CC5. UL SA transmission to A-UE₂ is in theprimary DL CC 627 and in the secondary DL CC 629. After the UL SAs areencoded, scrambling, modulation, interleaving, and RE-mapping follow ineach DL CC, 631, 632, 633, 634, and 635.

For the mapping of the PHICH resources to DL CCs, three cases areidentified. The first case is the extension of a single DL CC and asingle UL CC to an equal number of multiple DL CCs and multiple UL CCswith a one-to-one mapping (link) between an UL CC and a DL CC asillustrated in FIG. 7. UL CC1 710, UL CC2 720, UL CC3 730, and UL CC4740 are respectively associated with DL CC1 715, DL CC2 725, DL CC3 735,and DL CC4 745. The PHICH resources in each DL CC are determined basedon the same mapping to the UL PRB, in the respective UL CC, and CSI asthe one described in Equation (1) and Equation (2) for legacy-UEs.Therefore, when an UL CC is uniquely mapped to a DL CC, the inventionassumes that the PHICH transmission is only in that DL CC and the samemapping applies for the PHICH resources as in the case of single DL CCand single UL CC. This determination of the PHICH resources appliesregardless of whether the UL SA is transmitted over one or multiple DLCCs or whether the PUSCH is transmitted over one or multiple UL CCs.Alternatively, the PHICH transmission is in the DL CC providing the ULSA for the respective PUSCH transmission by the advanced-UE. Therefore,if the UL SA scheduling PUSCH transmission in UL CC1 was obtained in DLCC2, the respective PHICH transmission is in DL CC2.

The second case considers that more than one UL CCs are associated witha single DL CC as illustrated in FIG. 8 where UL CC1 810 and UL CC2 820are linked with DL CC 815. For advanced-UEs, the number of PRBs in allthese UL CCs should be jointly considered when determining the PHICHresources in the DL. If the number of PRBs in the UL CC1 is N_(RB)^(UL1) and the number of PRBs in UL CC2 is N_(RB) ^(UL2) then, for thepurposes of PHICH mapping, the PRBs in UL CC2 can be numbered fromN_(RB) ^(UL1) up to N_(RB) ^(UL1)+N_(RB) ^(UL2)−1. This can be indicatedto advanced-UEs through broadcast signaling or through UE-specifichigher layer signaling such as Radio Resource Control (RRC) signaling.For legacy-UEs, the PHICH resource mapping can be as previouslydescribed. If legacy-UEs are supported in both UL CCs, using the samePHICH resource mapping as in the case of a single UL CC linked to asingle DL CC may result in collisions of PHICH resources as the same PRBnumbering is used in each UL CC and the same broadcast channel isreceived from the single DL CC. To avoid this problem, the Node Bscheduler can assign to legacy-UEs the two parameters determining thePHICH resource, namely the first PRB of the PUSCH transmission and theCSI, so that legacy-UEs having PUSCH transmissions in different UL CCsdo not have the same PHICH resource for the subsequent DL transmissionin the common DL CC.

The third case considers that more than one DL CCs are associated with asingle UL CC as illustrated in FIG. 9 where DL CC1 910 and DL CC2 920are linked to UL CC 915. If legacy-UEs are linked to either DL CC1 or DLCC2, the ones linked to DL CC1 have the respective PHICH transmissionsin DL CC1 and the ones linked to DL CC2 have the respective PHICHtransmissions in DL CC2. The required PHICH resources will beapproximately doubled but no modifications to the conventional PHICHresource mapping method are needed. For advanced-UEs, the DL CC carryingthe PHICH transmission is the primary DL CC.

If legacy-UEs are linked only to DL CC1, and DL CC2 is used exclusivelyby advanced-UEs, then, in order to minimize the PHICH overhead, thePHICH transmission can be only in DL CC1 (no PHICH is transmitted in DLCC2), and the respective PHICH resource mapping can be as previouslydescribed. The advanced-UEs can be notified that PHICH transmission isonly in DL CC1 either through additional bits in a broadcast channeltransmitted in DL CC1 and/or DL CC2 or through RRC signaling. If onlyadvanced-UEs exist in the communication system, the PHICH transmissioncan be configured in the same manner (as in the case where legacy UEsare linked only to DL CC1). In this case, DL CC2 has no PHICHtransmissions.

The baseline setups in FIG. 8 and FIG. 9 can be generalized to includemore DL CCs and/or more UL CCs. Such a generalization is illustrated inFIG. 10 wherein the communication system includes 3 DL CCs, 1010, 1020,and 1030 and 2 UL CCs, 1015 and 1025. Legacy-UEs are assumed to have oneDL CC linked to one UL CC. If legacy-UEs have PUSCH transmissions inboth UL CC1 and UL CC2, the respective PHICH transmissions are in DL CC1and DL CC2 and the conventional PHICH resource mapping applies. Foradvanced-UEs, DL CC3 may not contain any PHICH transmission and this isindicated either through broadcast or through dedicated signaling aspreviously described. If legacy-UEs have PUSCH transmissions only in ULCC 1 or if legacy-UEs do not exist, the PHICH transmission toadvanced-UEs can be only in DL CC1, if the PRBs for the UL CCs arejointly considered for the purposes of PHICH resource mapping asdescribed in FIG. 8. Otherwise, the PHICH transmission can be in both DLCC1 and DL CC2 as described in FIG. 9.

A 2-bit HARQ-ACK signal transmission on the PHICH in response to a PUSCHtransmission consisting of two CWs (or two TBs) from an advanced-UEusing Spatial Multiplexing (SM) from at least 2 UE transmitter antennas,with each CW (or TB) having a separate HARQ process, can be supported bymodifying the conventional PHICH mapping method and imposing some minorrestrictions on the number of PRBs for the PUSCH transmission. Assumingthat SDMA is not applied and that at least 2 PRBs are used by the PUSCHtransmission, the PHICH resources for the first and second HARQ-ACK bitsof the respective first and second CWs or TBs can be respectivelyderived from the first and second PRBs of the PUSCH transmission.Therefore, for the PHICH transmission of the first HARQ-ACK bit, thePHICH group number and the orthogonal sequence index are determined asin Equation (1) and Equation (2). For the PHICH transmission of thesecond HARQ-ACK bit, the PHICH group number n_(PHICH) ^(group) and theorthogonal sequence index n_(PHICH) ^(seq) are respectively determinedby Equation (3).

n _(PHICH) ^(group)=(I _(PRB) _(—) _(RA) ^(lowest) ^(—)^(index)+1+CSI)mod N _(PHICH) ^(group) and n _(PHICH) ^(seq)=(└I _(PRB)_(—) _(RA) ^(lowest) ^(—) ^(index)+1)/N _(PHICH) ^(group) ┘+CSI)mod 2N_(SF) ^(PHICH)  (3)

Alternatively, the resources for the 2-bit HARQ-ACK signal transmissioncan be determined assuming that the RS transmission from the first ofthe at least 2 UE transmitter antennas uses a first CSI, CSI₁, and theRS transmission from the second of the at least 2 UE transmitterantennas uses a second CSI, CSI₂. Only the first CSI, CSI₁, may beprovided by the CSI IE of the UL SA and the second CSI, CSI₂, may beimplicitly determined based on the value of the first CSI. Then, thePHICH group number and the orthogonal sequence index for thetransmission of the first HARQ-ACK bit and of the second HARQ-ACK bitare respectively determined using Equation (1) and Equation (2) wherethe first CSI value, CSI₁, and the second CSI value, CSI₂, respectivelyapply.

The above PHICH resources for the first and second HARQ-ACK bits may belocated in different REGs and therefore, the receiver of an advanced-UEsupporting transmission of 2 CWs (or 2 TBs) may be required to monitor 2REGs for the respective PHICH detection. To avoid increasing thecomplexity of the advanced-UE receiver with respect to the PHICHdetection, if the PUSCH transmission can be mandated to use at leastN_(PHICH) ^(group)+1 PRBs, the PHICH resources for the 2-bit HARQ-ACKsignal transmission can always be located in the same REG. If the firstand second PRBs map to the same PHICH group, the above PHICH mappingapplies. However, if the first and second PRBs map to different PHICHgroups, as is typically the case, the above PHICH mapping rule ismodified so that the PHICH resources for the first and second HARQ-ACKbits are respectively determined from the first and N_(PHICH) ^(group)+1assigned PRBs, instead of the first and second PRBs, without increasingthe total required PHICH resources. Therefore, in the latter case, thePHICH group number N_(PHICH) ^(group) and the orthogonal sequence indexn_(PHICH) ^(seq) for the transmission of the second HARQ-ACK bit isdetermined by Equation (4) and Equation (5).

n _(PHICH) ^(group)=(I _(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index) +N_(PHICH) ^(group) +CSI)mod N _(PHICH) ^(group)  (4)

n _(PHICH) ^(seq)=(└I _(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index) +N_(PHICH) ^(group))/N _(PHICH) ^(group) ┘+CSI)mod 2N _(SF) ^(PHICH)  (EQ5)

With the above mapping, the Node B scheduler may also schedule the PUSCHtransmission so that the 2-bit HARQ-ACK signal transmission is in thesame QPSK symbol, thereby eliminating detection problems that may becaused by having different transmission power between the I-branch andthe Q-branch.

If SDMA is applied to PUSCH transmissions among N_(SDMA) advanced-UEsand the CSI consists of N_(CSI) bits then, to accommodate PHICH mappingfor the transmission of 2 CWs (or 2 TBs) in the PUSCH, it is requiredthat the PUSCH transmission is greater than at least 2·N_(SDMA) PRBs inorder to avoid collisions of PHICH resources. It is also required thatN_(SDMA)≦2^(N) ^(CSI) in order to uniquely differentiate the PHICHresources for each SDMA UE. The PHICH resources for the 2-bit HARQ-ACKsignal transmission to the advanced-UE having assigned CSI=0 can bederived from the first and second PRBs of the PUSCH transmission, thePHICH resources for the 2-bit HARQ-ACK transmission to the advanced-UEhaving assigned CSI=1 can be derived from the third and fourth PRBs ofthe PUSCH transmission, and so on.

When applying SDMA among UEs having PUSCH transmission with 2 CWs (or 2TBs) and UEs having PUSCH transmission with 1 CW (or) 1 TB), the formerUEs need to assume that all UEs have PUSCH transmission of 2 CWs (or 2TBs). Then, by assigning the smaller CSI values to UEs having PUSCHtransmission with 1 CW (or 1 TB), collisions of PHICH resources can beavoided at the expense of some small PHICH resource overhead. Therefore,an advanced-UE having transmission of 2 CWs (or 2 TBs) determines thePHICH group number for the transmission of the first ACK/NAK bit byEquation (6a)

n _(PHICH) ^(group)=(I _(PRB) _(—) _(RA) ^(lowest) ^(—)^(index)+2·CSI)mod N _(PHICH) ^(group)  (6a)

The orthogonal sequence index within the group is determined by Equation(7a).

n _(PHICH) ^(seq)=(└I _(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index) /N_(PHICH) ^(group)┘+2·CSI)mod 2N _(SF) ^(PHICH)  (7a)

The PHICH group number for the transmission of the second HARQ-ACK bitis determined by Equation (6b).

n _(PHICH) ^(group)=(I _(PRB) _(—) _(RA) ^(lowest) ^(—)^(index)+2·CSI+1)mod 2N _(SF) ^(PHICH)  (6a)

The orthogonal sequence index within the group is determined by Equation(7b).

n _(PHICH) ^(seq)=(└I _(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index) /N_(PHICH) ^(group)┘+2·CSI+1)mod 2N _(SF) ^(PHICH)  (7b)

A first PHICH resource mapping for PUSCH transmission consisting of 2CWs (or of 2 TBs) is illustrated in FIG. 11 assuming N_(PHICH)^(group)=1, N_(SF) ^(PHICH)=4, and I_(PRB) _(—) _(RA) ^(lowest) ^(—)^(index)=0. UE1 1110 transmits 1 CW (or 1 TB) and is assigned CSI=0. Therespective PHICH resource 1115 for the 1-bit HARQ-ACK signaltransmission is resource 0. UE1 1120 transmits 1 CW (or 1 TB) and isassigned CSI=1. The respective PHICH resource 1125 for the 1-bitHARQ-ACK signal transmission is resource 1. UE3 1130 transmits 2 CWs (or2 TBs) and is assigned CSI=2. The respective PHICH resources 1135 forthe 2-bit HARQ-ACK signal transmission are resources 4 and 5. UE4 1140transmits 2 CWs (or 2 TBs) and is assigned CSI=3. The respective PHICHresources 1145 for the 2-bit HARQ-ACK signal transmission are resources6 and 7. It can be observed that UE3 and UE4, assigned respectivelyCSI=2 and CSI=3, assume that UE1 and UE2, assigned respectively CSI=0and CSI=1, also transmit 2 CWs (or 2 TBs). This leads to the PHICHresources 2 and 3 being unused but avoids any collision of PHICHresources. Note that under the restriction of having the PUSCHtransmission over at least 2·(N_(PHICH) ^(group)+N_(SDMA)) PRBs, bothHARQ-ACK bits may be transmitted in the same PHICH group as for thenon-SDMA case by simply modifying the PHICH resources for thetransmission of the second HARQ-ACK bit as previously described.

A second PHICH resource mapping for PUSCH transmission consisting of 2CWs (or 2 TBs) is illustrated in FIG. 12 assuming N_(PHICH) ^(group)=1,N_(SF) ^(PHICH)=4, and I_(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index)=0. UE11210 transmits 1 CW (or 1 TB) and is assigned CSI=0. The respectivePHICH resource 1215 for the 1-bit HARQ-ACK signal transmission isresource 0. UE2 1220 transmits 1 CW (or 1 TB) and is assigned CSI=1. Therespective PHICH resource 1225 for the 1-bit HARQ-ACK signaltransmission is resource 1. UE3 1230 transmits 2 CWs (or 2 TBs) and isassigned CSI=2 and CSI=3 for the RS transmission from a first UE antennaand from a second UE antenna, respectively (the UE is assumed to have atleast 2 transmitter antennas in conjuction with the application of SM).The respective PHICH resources 1235 for the 2-bit HARQ-ACK signaltransmission are resources 2 and 3 respectively determined from CSI=2and CSI=3. UE4 1240 transmits 2 CWs (or 2 TBs) and is assigned CSI=4 andCSI=5. The respective PHICH resources 1245 for the 2-bit HARQ-ACK signaltransmission are resources 4 and 5. It can be observed that unlike thefirst PHICH resource mapping, UE3 and UE4 need not be aware of thepresence of other UEs and PHICH resource waste need not occur.

An alternative to the explicit 2-bit HARQ-ACK signal transmission is tobundle the 2 bits into 1 bit with ACK being transmitted if both CWs (orboth TBs) are received correctly and NAK being transmitted otherwise.The tradeoff to the decreased PHICH overhead is the reduced efficiencyof the HARQ operation as a correctly received CW (or TB) needs to beretransmitted if the other CW (or TB) is not correctly received.

For legacy communication systems, the number of PHICH groups N_(PHICH)^(group) is assumed to be given by N_(PHICH) ^(group)=┌N_(g)(N_(RB)^(UL)/8)┐ as was previously described. The reason for associatingN_(PHICH) ^(group) with N_(RB) ^(DL), instead of the total number of ULPRBs N_(RB) ^(UL), is to reduce the amount of information that needs tobe most often broadcasted (P-BCH). Legacy-UEs are assumed to know onlyN_(RB) ^(DL) before having to receive the PHICH and N_(RB) ^(UL) issubsequently obtained. Although using N_(RB) ^(DL), instead of N_(RB)^(UL), to set the number of PHICH groups may be reasonable for legacycommunication systems because N_(RB) ^(DL) and N_(RB) ^(UL) have similarvalues due to mostly symmetric traffic, such as for Voice over InternetProtocol (VoIP) services, the PHICH overhead becomes substantial whenN_(RB) ^(DL) is several times greater than N_(RB) ^(UL), as may often bethe case for advanced communication systems supporting data serviceshaving asymmetric traffic distributions. The discrepancy in the N_(RB)^(DL) and N_(RB) ^(UL) values is further exacerbated by the fact thatseveral UL PRBs are used for PUCCH transmission and, therefore, will notbe actually used for PHICH mapping. For example, for N_(RB)^(DL)=4N_(RB) ^(UL) a PHICH resource is assigned for every UL PRB, evenfor N_(g)=1/6 assuming a REG multiplexing capacity of 8 PHICHs (2 fromI/Q times 4 from an orthogonal sequence with N_(SF) ^(PHICH)=4).Furthermore, if the number of PUCCH PRBs is N_(RB) ^(PUCCH)=N_(RB)^(UL)/3, then there are more PHICH resources reserved than there arePRBs for PUSCH transmission.

To mitigate the overhead from over-dimensioning the PHICH resources, theinvention considers that for multiple DL CCs, a sub-set of these DL CCsare used to provide the initial access for both legacy-UEs andadvanced-UEs while the remaining DL CCs are used only after thecommunication link for an advanced-UE has been established. Theconventional process for setting up a communication link between a UEand its serving Node B includes the UE performing a cell search foracquiring a Synchronization CHannel (SCH) transmitted by the Node B,P-BCH and S-BCH reception for obtaining system information, transmissionof a Physical Random Access CHannel (PRACH) for enabling the Node B toacquire a signal from the UE, and reception of a Random Access CHannel(RACH) response assigning the parameters completing the setup.Therefore, the invention considers that channels associated with theinitial establishment of the communication link, such as the SCH, P-BCH,and PRACH, are transmitted only in a sub-set of DL CCs. Once the setupis complete, the serving Node B can inform the advanced-UE through RRCsignaling of a new DL/UL pair-band assignment and the advanced-UE canmove its link to the assigned pair-band. In this case, the PHICHduration and N_(g) value for PHICH transmission in the DL CC withouttransmission of channels associated with establishing the communicationlink is indicated to the advanced-UE through RRC signaling.

By using a sub-set of DL CCs to establish the communication link, theoverhead of the associated channels can be avoided in the remaining DLCCs. Moreover, additional optimizations can be performed in theremaining DL CCs as the constraints of having to support the initialcommunication setup are avoided. FIG. 13 further illustrates theprevious principles for an exemplary configuration of 2 DL CCs of 18 MHzeach, 1310 and 1340, and 2 UL CCs of 4.5 MHz each, 1320 and 1350. ThePUCCH is assumed to be transmitted at the two BW edges of the UL CC1,1330 and 1335, and UL CC2, 1360 and 1365. The communication setup isestablished in DL CC1 and UL CC1.

The number of PHICH groups in DL CC2 N_(PHICH) ^(group)=┌N_(g)^(new)(N_(RB) ^(UL)/8)┐ is determined based on N_(RB) ^(UL) for UL CC2and N_(g) ^(new) may be additionally specified and be different thanN_(g) to reflect potentially different PHICH resource requirements in DLCC1 and DL CC2 due to, for example, different BW sizes between UL CC1and UL CC2. The advanced-UEs may be notified of N_(RB) ^(UL) for UL CC2or of N_(g) ^(new) either through an S-BCH in DL CC1 or as part of theRRC signaling performing the pair-band assignment.

The advanced-UEs may also be notified, either through an S-BCH orthrough RRC signaling, to exclude the PRBs used for PUCCH transmissionfrom the determination of the PHICH resources. The PUCCH PRBs areassumed to be symmetrically placed on each side of the operating BW, asshown in FIG. 12, and their number N_(RB) ^(PUCCH) for each side of theoperating BW is assumed to be broadcasted by the Node B. Then, thenumber of PHICH groups is determined as N_(PHICH)^(group)=┌N_(g)((N_(RB) ^(UL)−2·N_(RB) ^(PUCCH))/8)┐, the PHICH groupnumber is determined as n_(PHICH) ^(group)=(I_(PRB) _(—) _(RA) ^(lowest)^(—) ^(index)−N_(RB) ^(PUCCH)+CSI)mod N_(PHICH) ^(group), and theorthogonal sequence index within the group is determined asn n_(PHICH)^(seq)=(└I_(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index)−N_(RB)^(PUCCH))/N_(PHICH) ^(group)┘+CSI)mod 2N_(SF) ^(PHICH).

Alternatively, the appropriate scaling of PHICH groups may be achievedby allowing a larger range for the N_(g) value used for advanced-UEsrelative to N_(g) value used by legacy-UEs. This can be achieved bysupplementing the N_(g) value used for legacy-UEs through thetransmission of additional bits in the P-BCH. These additional bits areinterpreted only by advanced-UEs. In general, assuming that from thelegacy-UEs perspective the P-BCH carries reserved bits in addition toinformation bits, some of these reserved bits can be used to broadcastinformation only to advanced-UEs. For example, referring to FIG. 14, ifthe total number of P-BCH information bits is 24 and legacy-UEs caninterpret only 16 of them 1410, the remaining 8 bits 1420 can be used tobroadcast additional information only to advanced-UEs for which theP-BCH can consist of up to 24 bits 1430. For PHICH transmission, if avalue of N_(g)ε{1/6,1/2,1,2} is signaled to legacy-UEs using 2 P-BCHbits, a value of N_(g)ε{1/18,1/12,1/8,1/6,1/2,1,2,4} can be signaled toadvanced-UEs using 3 P-BCH bits where 2 of these bits are the same onesused to signal the N_(g) value to legacy-UEs and the third bit is one ofthe reserved P-BCH bits.

While the present invention has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the appended claims.

What is claimed is:
 1. A method for a Node B to transmit anacknowledgement signal to a User Equipment (UE), the acknowledgementsignal indicating whether the Node B successfully received a data packettransmitted by the UE, the acknowledgement signal including twoinformation bits, the data packet including two transport blocks andeach information bit corresponding to each transport block, and the datapacket being transmitted from the UE over at least a first PhysicalResource Block (PRB) having an index I_(PRB) _(—) _(RA) ^(lowest) ^(—)^(index) and including a transmission time interval and a frequencyresource block, the method comprising the steps of: transmitting, by theNode B, an acknowledgement signal corresponding to a first transportblock using a first resource that is determined based on the indexI_(PRB) _(—) _(RA) ^(lowest) ^(—) ^(index); and transmitting, by theNode B, an acknowledgement signal corresponding to a second transportblock using a second resource that is determined based on I_(PRB) _(—)_(RA) ^(lowest) ^(—) ^(index)+1.